The prior art describes many devices and processes allowing such a separation to be performed.
The most simple technique consists in introducing the mixture to be separated into a chamber whose volume is designed to allow a sufficient residence time for all the drops forming the dispersed phase to have time to gather and coalesce at the separation interface between the two phases.
This technique, which is commonly used, involves very bulky installations and possibly relatively long residence times.
An improvement in this technique consists in heating the chambers containing the mixture so as to increase the rate of sedimentation of the drops and their encounter probability.
Another technique consists in applying an electric field which promotes the coalescence of the drops of a conducting dispersed phase in a relatively little conducting medium.
In the electrostatic separators applying this principle, breakdown phenomena a due to an increase in the electric charge between the electrodes may sometimes be observed, for example in case of an alignment of conducting drops in line with the field.
Other electrode and electric field separator technologies are described in patents U.S. Pat. Nos. 4,601,834, 1,592,011, SU-1,568,741.
The separation between two phases may be improved by using the effect of a centrifugal acceleration, as described in patent FR-2,663,238 filed by the applicant, and by promoting the formation of a film of drops which have coalesced on the surface of the inner helical part of the device.
Patent U.S. Pat. No. 4,116,670 describes a device for achieving the coalescence of drops between two electrodes until drops of a determined size are obtained, the separation of the drops being performed in a centrifugal separator located after the zone of the device achieving the coalescence of the drops.
Patent application FR-92/13,360 filed by the applicant describes a device using the combined effects of the electrocoalescence due to the presence of an electric field between two electrodes and of the centrifugal effect resulting from the shape of the electrodes to promote the phase separation.
It has been discovered, and this is the object of the present invention, that it is possible and advantageous to benefit by the simultaneous action of an electric field and of a centrifugal effect for separating a mixture, by using electrodes of a simple shape, the centrifugal effect being due to the tangential introduction of the mixture and to its flowing inside a revolution volume delimited by the electrodes.
In the text hereafter, the term electrode is understood to be a part brought to an electric potential.